As introduced by IEEE Trans. Wireless Commun., vol. 9, no. 11, pp. 3590-3600, 2010, by providing hundreds of antennas at a base station to serve tens of UEs simultaneously in the same time-frequency resource blocks, a massive MIMO system can greatly improve spectrum efficiency and energy radiation efficiency of a cellular network. In general, such massive MIMO system operates in a Time Division Duplex (TDD) mode, so as to utilize reciprocity between uplink and downlink channels to obtain Channel State Information (CSI) based on orthogonal uplink trainings, thereby significantly reducing pilot overheads due to channel training (the optimal pilot-based channel training requires orthogonality between pilot sequences transmitted from different antennas and thus a pilot length larger than or equal to the total number of transmitting antennas). The base station performs multi-user detection (in the uplink) or precoding (in the downlink) based on the estimated CSI to obtain a multiplexing gain or an array gain, thereby improving the effectiveness and reliability of information transmission. However, when the base station needs to broadcast control signaling or page inactive UEs, it cannot obtain the multiplexing gain or array gain due to lack of CSI for these UEs. On the other hand, in this case the orthogonal uplink channel trainings are not applicable (as it is impossible to guarantee the orthogonality between pilot sequences for different UEs when they are selected by the UEs autonomously). The pilot and feedback overheads for orthogonal downlink channel trainings are too costly to be acceptable. Hence, the transmission of broadcast signaling becomes quite challenging.